1. Technical Field
The technical field relates to an electrochemical capacitor to be used for regenerating a backup power supply of electronic devices, hybrid cars, and fuel-cell powered cars, or for storing electric power.
2. Background Art
FIG. 5A is a horizontal sectional view of a conventional electrochemical capacitor. FIG. 5B is a partially cutaway front view of electrode wound unit 100 of the conventional electrochemical capacitor.
The conventional electrochemical capacitor includes electrode wound unit 100, lithium metals (lithium electrodes) 104, 105, and outer container 106. Electrode wound unit 100 is formed of positive electrode 101, negative electrode 102, and separator 103 disposed between electrodes 101 and 102. These elements are layered and wound together concentrically, thereby forming electrode wound unit 100. Lithium metals 104 and 105 are disposed as lithium-ion suppliers on the outer periphery and the center of electrode wound unit 100, respectively. Electrode wound unit 100, lithium metals 104, 105, and electrolytic solution (not shown) are accommodated in outer container 106 made of aluminum or iron.
Each of positive electrode 101 and negative electrode 102 includes a collector as a core member, and the collector is made of porous material having holes penetrating through the material from the front face to the rear face. The collector will be detailed later. Use of the porous collector enables the lithium ions to move freely from lithium metals 104 and 105 through the holes of the respective collectors of positive electrode 101 and negative electrode 102 although lithium metals 104 and 105 are disposed separately on the outer periphery and at the center of electrode wound unit 100. This structure thus allows every portion of negative electrode 102 of electrode wound unit 100 to be pre-doped in advance with the lithium ions.
The collectors of positive electrode 101 and negative electrode 102 are respectively connected with electrode terminals 107, 108, which are led out in opposite directions from each other and along a winding axis direction of cylindrical electrode-wound unit 100. Lithium metal 105 disposed at the center of electrode wound unit 100 is supported by tubular stick 109 that also works as a shaft stick for supporting electrode wound unit 100.
The outermost face of electrode wound unit 100 is rigidly taped up with tape 110 in order to keep the unit 100 wound.
As discussed above, the foregoing conventional electrochemical capacitor includes two lithium-ion suppliers, i.e. one on the outer periphery and the other at the center of electrode wound unit 100. This structure allows pre-doping negative electrode 102 with the lithium ions faster than a structure where one lithium-ion source supplies the lithium ions for pre-doping.